1. Field of the Invention
The present invention generally relates to a device and method for depicting cardiac position and motion. More specifically, the present invention relates to a device and non-radiographic, non-ultrasound, and non-electrocardiogram method of depicting cardiac position and motion.
2. Description of Related Art
During the aging process, weakened or ineffective cardiac muscles may inhibit the cardiac pumping function from either the right, left, or both ventricles. When the pumping activity of the heart cannot meet the body's demands, systemic shock and subsequent organ dysfunction (such as pulmonary edema and renal failure) can result. Weakened heart muscles can also result in an over distended, dilated myocardium, which can have a detrimental effect on the electrical conduction and overall mechanical performance of the heart.
Advances in medical science have attempted to overcome these problems by replacing an impaired heart via heart transplants, or with devices such as artificial hearts. However, heart transplants are difficult to obtain since there is a limited donor supply. Moreover, artificial hearts have proved not entirely effective in duplicating cardiac contractions, are extremely expensive, and are known to be rejected by the human body.
Therefore, rather than replacing the heart, various arrangements have been proposed to assist right and left ventricular output of the existing impaired heart. For example, a number of arrangements are suggested in U.S. Pat. No. 4,621,617 to Sharma (“the '617 patent). FIG. 1 of the '617 patent proposes an arrangement in which two components are disposed in surrounding relation to the heart and function to compress the heart therebetween to assist ventricular output thereof. The two components are furnished with electromagnetic induction circuitry, numerous pole elements, and are secured to one another by a mechanical hinge. It can be appreciated that the device is quite cumbersome, difficult to implant, and has achieved little if any acceptance. FIG. 4 of the '617 patent illustrates an alternate arrangement in which a compressor element is provided posteriorly to the heart and is movable to compress the heart against the rib cage. This embodiment is somewhat more practical, but nevertheless problematic in a number of respects. For example, no means are provided for evaluating the amount of compressive resistance or intra-cardiac pressure of the heart during compression thereof. As a result, the compressor element may either apply insufficient compressive force to the heart, thereby resulting in ineffective ventricular assist, or apply excessive compressive force, thereby damaging the heart. Additionally, providing a compressor element posteriorly to the heart requires complex surgery in which the entire chest cavity must be opened. Moreover, such placement of the compressor element is largely impractical since the aorta, esophagus and spine are all disposed in close proximity to the posterior portion of the heart and leave little room for insertion of any type of assist device.
U.S. Pat. No. 5,498,228 (“the '228 patent”), which is incorporated herein by reference in its entirety, describes an electromagnetic biventricular device that includes an electromagnetic coil that is placed on the anterior chest. When current is passed through the coil, an electromagnetic field is generated posteriorly though the sternum so that the field interfaces with a magnetic field of a magnetic mat that resides on the anterior aspect of the heart. When like poles of the electromagnetic field and the magnetic mat interface, there is a posterior displacement of the magnetic mat on the heart. This takes place during systole. The '228 patent discloses the use of an EKG to assist with the operation of the device.
Present imaging modalities of the heart, which may use radiography, ultrasound, and/or electrocardiograms, are useful to guide intervention in the treatment of various cardiac diseases. These imaging modalities are anatomic and functional. Understanding cardiac contractility in a real-rime fashion may be useful information in guiding therapy with the devices described above.